Transfection ofActinomycesspp. by Genomic DNA of Bacteriophages from Human Dental Plaque

Abstract

Bacteriophages that produced turbid or clear zones of lysis in strains ofActinomyceswere isolated from 22 of 124 samples of fresh human dental plaque. All human and nonhuman strains ofActinomyces viscosusorActinomyces naeslundiitested in this study were sensitive to infection by one or more of these phages. In contrast, none of theActinomyces odontolyticus, Actinomyces israelii,orActinomyces bovisstrains tested were susceptible. Results of restriction endonuclease analyses indicated that the genomes of these phages consisted of double-stranded DNA molecules ranging in size between 16 and 60 kbp. Sequence homology under hybridization conditions of high stringency was observed among a few of the isolated phages. A lysogenized isolate ofA. viscosusMG-1 was obtained following infection with a temperate phage, designated φ225. Results of Southern blot analyses indicated that φ225 replicated as a plasmid in the lysogenized strain. Genomic DNA from several lytic phages was used to establish conditions for transfection by electroporation of strains ofActinomycesspp. Efficiencies of DNA transfer ranged from 102to 105plaque-forming units per microgram of DNA were obtained under optimal transfection conditions. The results of these studies demonstrate that transfer of genetic information inActinomycesspp. can be achieved by transfection.